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Gilbert DF, Friedrich O, Wiest J. Assaying Proliferation Characteristics of Cells Cultured Under Static Versus Periodic Conditions. Methods Mol Biol 2023; 2644:35-45. [PMID: 37142914 DOI: 10.1007/978-1-0716-3052-5_3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
Two-dimensional in vitro culture models are widely being employed for assessing a vast variety of biological questions in different scientific fields. Common in vitro culture models are typically maintained under static conditions, where the surrounding culture medium is replaced every few days-typically every 48 to 72 h-with the aim to remove metabolites and to replenish nutrients. Although this approach is sufficient for supporting cellular survival and proliferation, static culture conditions do mostly not reflect the in vivo situation where cells are continuously being perfused by extracellular fluid, and thus, create a less-physiological environment. In order to evaluate whether the proliferation characteristics of cells in 2D culture maintained under static conditions differ from cells kept in a dynamic environment, in this chapter, we provide a protocol for differential analysis of cellular growth under static versus pulsed-perfused conditions, mimicking continuous replacement of extracellular fluid in the physiological environment. The protocol involves long-term life-cell high-content time-lapse imaging of fluorescent cells at 37 °C and ambient CO2 concentration using multi-parametric biochips applicable for microphysiological analysis of cellular vitality. We provide instructions and useful information for (i) the culturing of cells in biochips, (ii) setup of cell-laden biochips for culturing cells under static and pulsed-perfused conditions, (iii) long-term life-cell high-content time-lapse imaging of fluorescent cells in biochips, and (iv) quantification of cellular proliferation from image series generated from imaging of differentially cultured cells.
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Affiliation(s)
- Daniel F Gilbert
- Institute of Medical Biotechnology, Department of Chemical and Biological Engineering (CBI), Friedrich-Alexander-University Erlangen-Nürnberg, Erlangen, Germany.
| | - Oliver Friedrich
- Institute of Medical Biotechnology, Department of Chemical and Biological Engineering (CBI), Friedrich-Alexander-University Erlangen-Nürnberg, Erlangen, Germany
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Joshi P, Patel R, Kang SY, Serbinowski E, Lee MY. Establishment of ion channel and ABC transporter assays in 3D-cultured ReNcell VM on a 384-pillar plate for neurotoxicity potential. Toxicol In Vitro 2022; 82:105375. [PMID: 35550413 DOI: 10.1016/j.tiv.2022.105375] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2021] [Revised: 04/05/2022] [Accepted: 05/03/2022] [Indexed: 10/18/2022]
Abstract
Neurotoxicity potential of compounds by inhibition of ion channels and efflux transporters has been studied traditionally using two-dimensionally (2D) cultured cell lines such as CHO and HEK-293 overexpressing the protein of interest. However, these approaches are time consuming and do not recapitulate the activity of ion channels and efflux transporters indigenously expressed in neural stem cells (NSCs) in vivo. To overcome these issues, we established ion channel and transporter assays on a 384-pillar plate with three-dimensionally (3D) cultured ReNcell VM and demonstrated high-throughput measurement of ion channel and transporter activity. RNA sequencing analysis identified major ion channels and efflux transporters expressed in ReNcell VM, followed by validating 3D ReNcell-based ion channel and transporter assays with model compounds. Major ion channel activities were measured by specifically inhibiting potassium channels Kv 7.2 with XE-991 and Kv 4.3 with fluoxetine, and a calcium channel with 2-APB. Activities of major efflux transporters, MDR1, MRP1, and BCRP, were assessed using their respective blockers, verapamil, probenecid, and novobiocin. From this study, we demonstrated that 3D-cultured ReNcell VM on the 384-pillar plate could be a good alternative to rapidly identify environmental chemicals and therapeutic compounds for their role in modulating the activity of ion channels and efflux transporters, potentially leading to neurotoxicity.
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Affiliation(s)
- Pranav Joshi
- Department of Chemical and Biomedical Engineering, Cleveland State University, Cleveland, OH, USA; Bioprinting Laboratories Inc, Denton, TX, USA
| | - Rushabh Patel
- Department of Chemical and Biomedical Engineering, Cleveland State University, Cleveland, OH, USA; College of Medicine and Life Sciences, University of Toledo, Toledo, OH, USA
| | - Soo-Yeon Kang
- Department of Chemical and Biomedical Engineering, Cleveland State University, Cleveland, OH, USA; Department of Biomedical Engineering, University of North Texas, Denton, TX, USA
| | - Emily Serbinowski
- Department of Chemical and Biomedical Engineering, Cleveland State University, Cleveland, OH, USA; College of Medicine and Life Sciences, University of Toledo, Toledo, OH, USA
| | - Moo-Yeal Lee
- Department of Chemical and Biomedical Engineering, Cleveland State University, Cleveland, OH, USA; Department of Biomedical Engineering, University of North Texas, Denton, TX, USA.
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Gilbert DF, Mofrad SA, Friedrich O, Wiest J. Proliferation characteristics of cells cultured under periodic versus static conditions. Cytotechnology 2018; 71:443-452. [PMID: 30515656 DOI: 10.1007/s10616-018-0263-z] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2018] [Accepted: 09/27/2018] [Indexed: 12/13/2022] Open
Abstract
In vitro culture models have become an indispensable tool for assessing a vast variety of biological questions in many scientific fields. However, common in vitro cultures are maintained under static conditions, which do not reflect the in vivo situation and create a non-physiological environment. To assess whether the growth characteristics of cells cultured at pulsed-perfused versus static conditions differ, we observed the growth of differentially cultured cells in vitro by life-cell time-lapse imaging of recombinant HEK293YFPI152L cells, stably expressing yellow fluorescent protein. Cells were grown for ~ 30 h at 37 °C and ambient CO2 concentration in biochips mounted into a custom-designed 3D printed carrier and were imaged at a rate of ten images per hour using a fluorescence microscope with environment control infrastructure. Cells in one chip were maintained under static conditions whereas cells in another chip were recurrently perfused with fresh media. Generated image series were quantitatively analyzed using a custom-modified cell detection software. Imaging data averaged from four biological replicates per culturing condition demonstrate that cells cultured under conventional conditions exhibit an exponential growth rate. In contrast, cells cultured in periodic mode exhibited a non-exponential growth rate. Our data clearly indicate differential growth characteristics of cells cultured under periodic versus static conditions highlighting the impact of the culture conditions on the physiology of cells in vitro.
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Affiliation(s)
- Daniel F Gilbert
- Institute of Medical Biotechnology, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany. .,Erlangen Graduate School in Advanced Optical Technologies (SAOT), Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany.
| | - Sepideh Abolpour Mofrad
- Institute of Medical Biotechnology, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany.,Erlangen Graduate School in Advanced Optical Technologies (SAOT), Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany
| | - Oliver Friedrich
- Institute of Medical Biotechnology, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany.,Erlangen Graduate School in Advanced Optical Technologies (SAOT), Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany
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Zwart R, Mazzo F, Sher E. Microtransplantation of human brain receptors into oocytes to tackle key questions in drug discovery. Drug Discov Today 2018; 24:533-543. [PMID: 30395928 DOI: 10.1016/j.drudis.2018.10.015] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2018] [Revised: 09/18/2018] [Accepted: 10/30/2018] [Indexed: 10/27/2022]
Abstract
It is important in drug discovery to demonstrate that activity of novel drugs found by screening on recombinant receptors translates to activity on native human receptors in brain areas affected by disease. In this review, we summarise the development and use of the microtransplantation technique. Native receptors are reconstituted from human brain tissues into oocytes from the frog Xenopus laevis where they can be functionally assessed. Oocytes microtransplanted with hippocampal tissue from an epileptic patient were used to demonstrate that new antiepileptic agents act on receptors in diseased tissue. Furthermore, frozen post-mortem human tissues were used to show that drugs are active on receptors in brain areas associated with a disease; but not in areas associated with side effects.
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Affiliation(s)
- Ruud Zwart
- Eli Lilly, Lilly Research Centre, Erl Wood Manor, Sunninghill Road, Windlesham, GU20 6PH, UK.
| | - Francesca Mazzo
- Eli Lilly, Lilly Research Centre, Erl Wood Manor, Sunninghill Road, Windlesham, GU20 6PH, UK
| | - Emanuele Sher
- Eli Lilly, Lilly Research Centre, Erl Wood Manor, Sunninghill Road, Windlesham, GU20 6PH, UK
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Contreras-Nuñez E, Blancas-Flores G, Cruz M, Almanza-Perez JC, Gomez-Zamudio JH, Ventura-Gallegosc JL, Zentella-Dehesa A, Roman-Ramos R, Alarcon-Aguilar FJ. Participation of the IKK-α/β complex in the inhibition of the TNF-α/NF-κB pathway by glycine: Possible involvement of a membrane receptor specific to adipocytes. Biomed Pharmacother 2018; 102:120-131. [PMID: 29550635 DOI: 10.1016/j.biopha.2018.03.048] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2017] [Revised: 03/07/2018] [Accepted: 03/09/2018] [Indexed: 12/11/2022] Open
Abstract
Glycine modulates inflammatory processes mediated by macrophages and adipocytes through decreasing the secretion of TNF-α, IL-6, and leptin, while increasing adiponectin. These effects have been associated with the inactivation of NF-κB in response to TNF-α, across an increase of its inhibitor IκB-α in adipocytes. However, glycine upstream mainly influences the IκB kinase (IKK) complex, a multi-protein kinase complex considered a critical point in regulation of the NF-κB pathway; whether that is responsible for the TNF-α-induced phosphorylation of IkB has not been explored. Additionally, although previous studies have described glycine interactions with specific receptors (GlyR) in different immune system cell types, it is currently unknown whether adipocytes present GlyR. In this research, participation of the IKK-α/β complex in the inhibition of the TNF-α/NF-κB pathway by glycine was evaluated and associated with the synthesis and secretion of inflammatory cytokines in 3T3-L1 adipocytes. Furthermore, we also explored GlyR expression, its localization on the plasmatic membrane, intracellular calcium concentrations [Ca2+]i and strychnine antagonist action over the GlyR in these cells. Glycine decreased the IKK-α/β complex and the phosphorylation of NF-κB, diminishing the expression and secretion of IL-6 and TNF-α, but increasing that of adiponectin. GlyR expression and its fluorescence in the plasma membrane were increased in the presence of glycine. In addition, glycine decreased [Ca2+]i; whereas strychnine + glycine treatment inhibited the activation of NF-κB observed with glycine. In conclusion, the reduction of TNF-α and IL-6 and suppression of the TNF-α/NF-κB pathway by glycine may be explained in part by inhibition of the IKK-α/β complex, with a possible participation of GlyR in 3T3-L1 adipocytes.
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Affiliation(s)
- Erika Contreras-Nuñez
- Laboratorio de Farmacologia, Departamento de Ciencias de la Salud, DCBS, Universidad Autonoma Metropolitana-Iztapalapa (UAM-I), Avenida San Rafael Atlixco 186, A.P. 55-535, C.P. 09340, Mexico City, Mexico
| | - Gerardo Blancas-Flores
- Laboratorio de Farmacologia, Departamento de Ciencias de la Salud, DCBS, Universidad Autonoma Metropolitana-Iztapalapa (UAM-I), Avenida San Rafael Atlixco 186, A.P. 55-535, C.P. 09340, Mexico City, Mexico
| | - Miguel Cruz
- Unidad de Investigacion Medica en Bioquimica (UIM), Hospital de Especialidades, Centro Medico Nacional Siglo XXI. IMSS, Av. Cuauhtemoc 330, Col. Doctores, Del. Cuauhtemoc, Mexico City, Mexico
| | - Julio Cesar Almanza-Perez
- Laboratorio de Farmacologia, Departamento de Ciencias de la Salud, DCBS, Universidad Autonoma Metropolitana-Iztapalapa (UAM-I), Avenida San Rafael Atlixco 186, A.P. 55-535, C.P. 09340, Mexico City, Mexico
| | - Jaime H Gomez-Zamudio
- Unidad de Investigacion Medica en Bioquimica (UIM), Hospital de Especialidades, Centro Medico Nacional Siglo XXI. IMSS, Av. Cuauhtemoc 330, Col. Doctores, Del. Cuauhtemoc, Mexico City, Mexico
| | - Jose Luis Ventura-Gallegosc
- Departamento de Medicina Genomica y Toxicologia Ambiental, IIB, UNAM, SZ, CDMX, Mexico; Unidad de Bioquimica Instituto Nacional de Ciencias Medicas y Nutricion Salvador Zubiran, Mexico City Mexico
| | - Alejandro Zentella-Dehesa
- Departamento de Medicina Genomica y Toxicologia Ambiental, IIB, UNAM, SZ, CDMX, Mexico; Unidad de Bioquimica Instituto Nacional de Ciencias Medicas y Nutricion Salvador Zubiran, Mexico City Mexico
| | - Ruben Roman-Ramos
- Laboratorio de Farmacologia, Departamento de Ciencias de la Salud, DCBS, Universidad Autonoma Metropolitana-Iztapalapa (UAM-I), Avenida San Rafael Atlixco 186, A.P. 55-535, C.P. 09340, Mexico City, Mexico
| | - Francisco Javier Alarcon-Aguilar
- Laboratorio de Farmacologia, Departamento de Ciencias de la Salud, DCBS, Universidad Autonoma Metropolitana-Iztapalapa (UAM-I), Avenida San Rafael Atlixco 186, A.P. 55-535, C.P. 09340, Mexico City, Mexico.
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Kuenzel K, Mofrad SA, Gilbert DF. Phenotyping Cellular Viability by Functional Analysis of Ion Channels: GlyR-Targeted Screening in NT2-N Cells. Methods Mol Biol 2018; 1601:205-214. [PMID: 28470528 DOI: 10.1007/978-1-4939-6960-9_16] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Glycine receptor chloride channels (GlyRs) are attractive drug targets for therapeutic intervention and are also more and more recognized in the context of in vitro neurotoxicity and developmental neurotoxicity testing. Assaying the functional properties of GlyR can serve as an indicator of cellular viability and the integrity of the developing and mature central nervous system. Human pluripotent NTERA-2 (NT2) stem cells undergo neuronal differentiation upon stimulation with retinoic acid and express a large variety of neuronal proteins-including GlyR. YFP-I152L, a halide-sensitive variant of yellow fluorescent protein, allows high-throughput fluorescence-based functional analysis of GlyRs in NT2 cells. Here we describe a protocol for phenotyping of cellular viability by functional analysis of GlyR in neuronally differentiated NT2 (NT2-N) cells using YFP-I152L as a reporter of functional integrity of GlyRs. The protocol describes neuronal differentiation of NT2 stem cells, transient transfection of NT2-N cells with YFP-I152L as well as functional imaging and analysis of data from high-content imaging.
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Affiliation(s)
- Katharina Kuenzel
- Institute of Medical Biotechnology, Friedrich-Alexander-Universität Erlangen-Nürnberg, Paul-Gordan-Str. 3, 91052, Erlangen, Germany.
| | - Sepideh Abolpour Mofrad
- Institute of Medical Biotechnology, Friedrich-Alexander-Universität Erlangen-Nürnberg, Paul-Gordan-Str. 3, 91052, Erlangen, Germany
| | - Daniel F Gilbert
- Friedrich-Alexander University (FAU) Erlangen-Nürnberg, Institute of Medical Biotechnology, Paul-Gordan-Street 3, 91052, Erlangen, Germany
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Abstract
High-throughput cell viability assays are broadly used in RNAi and small molecule screening experiments to identify compounds that selectively kill cancer cells or as counter screens to exclude the compounds that have a generic effect on cell growth. While there are several assaying techniques available, cellular fitness is often assessed on the basis of one single and often rather indirect physiological indicator. This can lead to inconsistencies and poor correspondence between cell viability screening experiments, conducted under comparable conditions but with different viability indicators. Multiplexing, i.e., the combination of different individual assaying techniques in one experiment and subsequent comparative analysis of multiparametric data can decrease inter-assay variability and increase dataset concordance. Here, we describe a protocol for a multiplexing approach for high-throughput cell viability screening to address the issues encountered in the classical strategy using a single fitness indicator described above. The method combines a biochemical, luminescence-based approach and two fluorescence-based assay types. The biochemical method assesses cellular fitness by quantifying intracellular ATP concentration. Calcein labeling reflects cell fitness through membrane integrity and indirect measurement of ATP-dependent enzymatic esterase activity. Hoechst DNA stain correlates cell fitness with cellular DNA content. The presented multiplexing approach is suitable for low, medium and high-throughput screening and has the potential to decrease inter-assay variability and increase dataset concordance as well as reproducibility of experimental results.
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Lynch JW, Zhang Y, Talwar S, Estrada-Mondragon A. Glycine Receptor Drug Discovery. ADVANCES IN PHARMACOLOGY 2017; 79:225-253. [DOI: 10.1016/bs.apha.2017.01.003] [Citation(s) in RCA: 49] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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Step-by-step guide to building an inexpensive 3D printed motorized positioning stage for automated high-content screening microscopy. Biosens Bioelectron 2016; 92:472-481. [PMID: 27840039 DOI: 10.1016/j.bios.2016.10.078] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2016] [Revised: 10/21/2016] [Accepted: 10/25/2016] [Indexed: 01/16/2023]
Abstract
High-content screening microscopy relies on automation infrastructure that is typically proprietary, non-customizable, costly and requires a high level of skill to use and maintain. The increasing availability of rapid prototyping technology makes it possible to quickly engineer alternatives to conventional automation infrastructure that are low-cost and user-friendly. Here, we describe a 3D printed inexpensive open source and scalable motorized positioning stage for automated high-content screening microscopy and provide detailed step-by-step instructions to re-building the device, including a comprehensive parts list, 3D design files in STEP (Standard for the Exchange of Product model data) and STL (Standard Tessellation Language) format, electronic circuits and wiring diagrams as well as software code. System assembly including 3D printing requires approx. 30h. The fully assembled device is light-weight (1.1kg), small (33×20×8cm) and extremely low-cost (approx. EUR 250). We describe positioning characteristics of the stage, including spatial resolution, accuracy and repeatability, compare imaging data generated with our device to data obtained using a commercially available microplate reader, demonstrate its suitability to high-content microscopy in 96-well high-throughput screening format and validate its applicability to automated functional Cl-- and Ca2+-imaging with recombinant HEK293 cells as a model system. A time-lapse video of the stage during operation and as part of a custom assembled screening robot can be found at https://vimeo.com/158813199.
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Kuenzel K, Friedrich O, Gilbert DF. A Recombinant Human Pluripotent Stem Cell Line Stably Expressing Halide-Sensitive YFP-I152L for GABAAR and GlyR-Targeted High-Throughput Drug Screening and Toxicity Testing. Front Mol Neurosci 2016; 9:51. [PMID: 27445687 PMCID: PMC4923258 DOI: 10.3389/fnmol.2016.00051] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2016] [Accepted: 06/13/2016] [Indexed: 01/29/2023] Open
Abstract
GABAARs and GlyRs are considered attractive drug targets for therapeutic intervention and are also increasingly recognized in the context of in vitro neurotoxicity (NT) and developmental neurotoxicity (DNT) testing. However, systematic human-specific GABAAR and GlyR-targeted drug screening and toxicity testing is hampered due to lack of appropriate in vitro models that express native GABAARs and GlyRs. We have established a human pluripotent stem cell line (NT2) stably expressing YFP-I152L, a halide-sensitive variant of yellow fluorescent protein (YFP), allowing for fluorescence-based functional analysis of chloride channels. Upon stimulation with retinoic acid, NT2 cells undergo neuronal differentiation and allow pharmacological and toxicological evaluation of native GABAARs and GlyRs at different stages of brain maturation. We applied the cell line in concentration-response experiments with the neurotransmitters GABA and glycine as well as with the drugs strychnine, picrotoxin, fipronil, lindane, bicuculline, and zinc and demonstrate that the established in vitro model is applicable to GABAAR and GlyR-targeted pharmacological and toxicological profiling. We quantified the proportion of GABAAR and GlyR-sensitive cells, respectively, and identified percentages of approximately 20% each within the overall populations, rendering the cells a suitable model for systematic in vitro GABAAR and GlyR-targeted screening in the context of drug development and NT/DNT testing.
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Affiliation(s)
- Katharina Kuenzel
- Department of Chemical and Biological Engineering, Institute of Medical Biotechnology, Friedrich-Alexander-Universität Erlangen-NürnbergErlangen, Germany; Erlangen Graduate School in Advanced Optical Technologies, Friedrich-Alexander-Universität Erlangen-NürnbergErlangen, Germany
| | - Oliver Friedrich
- Department of Chemical and Biological Engineering, Institute of Medical Biotechnology, Friedrich-Alexander-Universität Erlangen-NürnbergErlangen, Germany; Erlangen Graduate School in Advanced Optical Technologies, Friedrich-Alexander-Universität Erlangen-NürnbergErlangen, Germany
| | - Daniel F Gilbert
- Department of Chemical and Biological Engineering, Institute of Medical Biotechnology, Friedrich-Alexander-Universität Erlangen-NürnbergErlangen, Germany; Erlangen Graduate School in Advanced Optical Technologies, Friedrich-Alexander-Universität Erlangen-NürnbergErlangen, Germany
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Towards in vitro DT/DNT testing: Assaying chemical susceptibility in early differentiating NT2 cells. Toxicology 2015; 338:69-76. [PMID: 26498558 DOI: 10.1016/j.tox.2015.10.007] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2015] [Revised: 10/15/2015] [Accepted: 10/15/2015] [Indexed: 11/21/2022]
Abstract
Human pluripotent embryonal carcinoma (NT2) cells are increasingly considered as a suitable model for in vitro toxicity testing, e.g. developmental toxicity and neurotoxicity (DT/DNT) studies, as they undergo neuronal differentiation upon stimulation with retinoic acid (RA) and permit toxicity testing at different stages of maturation. NT2 cells have recently been reported to show specific changes in dielectric resistance profiles during differentiation which can be observed as early as 24h upon RA-stimulation. These observations suggest altered susceptibility to chemicals at an early stage of differentiation. However, chemical susceptibility of early differentiating NT cells has not yet been studied. To address this question, we have established a cell fitness screening assay based on the analysis of intracellular ATP levels and we applied the assay in a large-scale drug screening experiment in NT2 stem cells and early differentiating NT2 cells. Subsequent analysis of ranked fitness phenotypes revealed 19 chemicals with differential toxicity profile in early differentiating NT2 cells. To evaluate whether any of the identified drugs have previously been associated with DT/DNT, we conducted a literature search on the identified molecules and quantified the fraction of chemicals assigned to the FDA (Food and Drug Administration) pregnancy risk categories (PRC) N, A, B, C, D, and X in the hit list and the small molecule library. While the fractions of the categories N and B were decreased (0.81 and 0.35-fold), the classes C, D and X were increased (1.35, 1.47 and 3.27-fold) in the hit list compared to the chemical library. From these data as well as from the literature review, identifying large fractions of chemicals being directly (∼42%) and indirectly associated with DT/DNT (∼32%), we conclude that our method may be beneficial to systematic in vitro-based primary screening for developmental toxicants and neurotoxicants and we propose cell fitness screening in early differentiating NT2 cells as a strategy for evaluating chemical susceptibility at different stages of differentiation to reduce animal testing in the context of the 3Rs.
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Yu R, Hurdiss E, Greiner T, Lape R, Sivilotti L, Biggin PC. Agonist and antagonist binding in human glycine receptors. Biochemistry 2014; 53:6041-51. [PMID: 25184435 DOI: 10.1021/bi500815f] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The human glycine receptor (hGlyR) is an anion-permeable ligand-gated channel that is part of a larger superfamily of receptors called the Cys-loop family. hGlyRs are particularly amenable to single-channel recordings, thus making them a model experimental system for understanding the Cys-loop receptor family in general. Understanding the relationship between agonist binding and efficacy in Cys-loop receptors should improve our future prospects for making specific agonists or antagonists. However, at present, there is no high-resolution structure for the complete hGlyR, and thus, modeling is needed to provide a physical framework on which to interpret single-channel data. The structure of the glutamate-gated chloride channel from Caenorhabditis elegans shows a much higher level of sequence identity to human hGlyR than previous templates such as AChBP or the bacterial channels, GLIC and ELIC. Thus, we constructed a model of the hGlyR and validated it against previously reported mutagenesis data. We used molecular dynamics to refine the model and to explore binding of both an agonist (glycine) and an antagonist (strychnine). The model shows excellent agreement with previous data but also suggests some unique features: (i) a water molecule that forms part of the binding site and allows us to account for some previous results that were difficult to reconcile, (ii) an interaction of the glycine agonist with S129, and (iii) an effect from E211, both of which we confirmed with new site-directed mutagenesis and patch clamp recordings. Finally, examination of the simulations suggests that strychnine binding induces movement to a conformational state distinct from the glycine-bound or apo state, not only within the ligand-binding domain but also in the transmembrane domain.
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Affiliation(s)
- Rilei Yu
- Structural Bioinformatics and Computational Biochemistry, Department of Biochemistry, University of Oxford , South Parks Road, Oxford OX1 3QU, United Kingdom
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